Blood Tests for Fragile X: The most accurate test available is the “FMR1 DNA Test” (sometimes called the “Fragile X DNA Test”) (the blood collection vial should have a purple lid).

Older testing using the chromosome (“cytogenetic”) test is not as accurate as the DNA test.Tests for Fragile X carried out before 1991 may not be correct and the results of cytogenetic tests since then may be inaccurate. People who were tested before 1991 or who have only had a cytogenetic test should have a DNA test.

Note: It is recommended that siblings of children with Fragile X be tested, even if they do not show signs of Fragile X, as they may be carriers. While some geneticists prefer to wait until siblings of individuals with Fragile X are considering having children before checking for the abnormality, many women who are carriers say that they would have preferred to be told between the ages of 10 and 13 years, when it is easier to have the conversation about "Mum's a carrier and she's okay, you're a carrier and you're okay". Then information about egg donation through IVF can be obtained by couples to assist with any reproductive decision-making.